Flaw detector for knitting machines and the like



March 28, 1961 R. e. RElP ,976,706

FLAW DETECTOR FOR KNITTING MACHINES AND THE LIKE Filed June 12, 1959 2 Sheets-Sheet 1 SUPP]. V

REVERS/A/G Sh/ITCH- C/RCU/T INV EN TOR.

R. G. REIP March 28, 1961 FLAW DETECTOR FOR KNITTING MACHINES AND THE LIKE 2 Sheets-Sheet 2 4' T I r 1 1 H .4

Filed June 12, 1959 ENTOR 94p c zyzzzozza G.%

iinited states FLAW DETECTOR FOR KNITTING MACHENES AND THE LIKE Filed June 12, 1959, Ser. No. 819,965

3 Claims. (Cl. 66-466) This invention relates to an improvement in a flaw detector for knitting machines of the type disclosed in the patent to Peck 2,694,911, issued November 23, 1954.

In the Peck patent, one or more nozzles are positioned in contact with a web of fabric being knitted and are arranged for transverse movement of the web, said nozzles directing compressed air against the web. The air flow rate is substantially constant as long as the fabric is free from flaws or defects, such as holes, or end outs. Upon occurrence of such a flaw, there will be sudden increase in air flow from the nozzle detecting such defect, which will cause operation of a switch means to stop the knitting machine, thus permitting correction of the condition causing the flaw. The device of the Peck patent, while basically sound, has been found to give less than satisfactory service under certain conditions of use. More particularly, its response characteristics are extremely sensitive so that even minor changes in web tension may cause operation of the device to effect machine stoppage.

The present invention represents an improvement over the device of the Peck patent, since it will provide machine stoppage only if a flaw of the type being guarded against actually develops in the material being knit. To achieve such results, means are provided to desensitize the device to minor variations in nozzle fiow rate, so that only major variations in flow rate, such as are associated with fabric flaws such as holes or end outs, will result in machine stoppage.

The main object of this invention is to provide an improvement in a flaw detector for knitting machines.

A more specific object is to provide a flaw detector for a knitting machine which will cause machine stoppage only when the type of fabric defect being guarded against is detected in the fabric.

Other objects and features of the invention will become more apparent from the following description and accompanying drawings wherein:

Fig. 1 is a schematic illustration of a combination of elements embodying the principles of the invention;

Fig. 2 is a View as generally seen from line 2--2 in Fig. 1;

Fig. 3 is a graph showing comparative response characteristics of a flaw detecting nozzle under two conditions of operation;

Fig. 4 is a plan view of one type of flaw detecting nozzle which may be used in the invention;

Fig. 5 is a section view as generally seen from line 5-5 in Fig. 4;

Fig. 6 is a plan view of another type of flaw detecting nozzle which may be used in the invention;

Fig. 7 is a section view as generally seen from line 77 in Fig. 6;

Fig. 8 is a section view as generally seen from line 88 in Fig. 6; and

Fig. 9 is a section view of a type of nozzle assemblage which may be used in the invention.

Referring now to the drawing, and more particularly to Fig. 1, a flaw detector representative of an embodiment 2,97%,735 Patented Mar. 28, 1961 of the invention, includes a sensing nozzle assemblage 10, a switch actuator in the form of a diaphragm assemblage l2, and an electric switch means 14. The nozzle assemblage 10, comprises a nozzle 16 which is positioned for engagement with the surface of a web of knitted fabric 18 which is being moved away from a knitting head of a knitting machine (not shown). The nozzle 16, is arranged for reciprocal transverse movement of the web 18, and for such purpose is mounted upon an L-shaped support 20 having two pair of rollers 22 which are adapted to embrace an L-shaped beam 24 which extends transverse of the web 18 and in spaced parallel relation thereto. Drive means for said nozzle 16 are provided which comprise an endless chain 26 atlixed to the support 20, which chain is mounted upon a pair of spaced sprocket wheels 28, one of which is rotated by means of an endless chain 30 driven by an electric motor 32. The latter is arranged for alternate rotation controlled by a reversing circuit including a pair of switches 34, each of which is sequentially engaged and operated by the nozzle 16 as it approaches the side edges of the web 18.

The nozzle 16, which may be of the type illustrated in Figs. 4 and 5, comprises a body portion 35 having an integral dome portion 36 projecting from the top surface thereof, and a pair of threaded openings 38 and 40. A first passageway 42 is arranged in the body portion 35, one end 43 of said passageway opening onto the center of the dome portion 36, the other end opening onto the threaded opening 38. The passageway 42 has an orifice defined by a reduced diameter portion 44 as shown. A second passageway 46 connects passageway 42 with the threaded opening 40. A compressed air delivery line or pipe 48 (Fig. 1) leading from a pressure source (not shown) and having a pressure regulator assembly 50, is affixed to the threaded opening 38, while a signal line or pipe 52 is affixed to threaded opening 4%.

The diaphragm assemblage 12 includes a housing 54 which positionally encloses a diaphragm 56 to form chambers 58 and 60. A desensitizing means in the form of an exterior volume chamber 62, connects the line 52 to the diaphragm chamber 60. Line 52 is also connected to the diaphragm chamber 58. A valve 64 is arranged to regulate air flow into volume chamber 62. A push rod 66 is afiixed at one end to the diaphragm 56, the other end of the rod projecting from the housing 54 to engage a contact arm 68 which is biased to open position and which forms part of the switch means 14. On the opposite side of the diaphragm 56 and in engagement therewith, is a compression spring 70, the degree of compression of which may be varied by an adjusting screw 72.

The electric switch means 14 allows arrangement of a DC. circuit to cause operation of a solenoid 74, upon seating of contact arm 63, whereby a pair of contact arms 76 will simultaneously disrupt an A.C. circuit which powers a knitting machine drive motor 78 and the motor 32, and also provide a holding circuit for the solenoid 74, all as seen in Fig. 1. A reset switch 80 is provided in the solenoid circuit, whereby the machine operator may reset the switch means 14 to effect operation of motors 32 and 78 after the condition producing a hole or end out in the knitted fabric is corrected. A warning signal, i.e., light or alarm, may be arranged in the solenoid circuit if desired, to warn the machine operator when a flaw is detected and the machine has been stopped.

From the foregoing description the operation of the device should be easily comprehendable. Assume that the air pressure in line 48 being delivered to the nozzle 16 is approximately 2 p.s.i. The normal back pressure in line 52 Will be somewhat less than 2 p.s.i. due to: pressure drop caused by orifice 44; the slow escape of air from the nozzle caused by the relative motion between the nozzle and the fabric passing thereover; the pressure of the fabric against the nozzle, which is a function of the web tension; and, the flow of air through the fabric interstices. Whatever the value of back pressure in line 52 happens to be, under normal operating conditions, such pressure will be the same after equalization, in diaphragm chambers 58 and 69 in volume chamber 62. Slight variations in such normal back pressure, due for example, to gradual changes in web tension, will cause like changes in pressure in diaphragm chambers 58 and 60 and in volume chamber 62.

The volume chamber 62 imposes a time lag whereby any variation in pressure line 52results in a change in pressure in diaphragm chamber 60 which follows change in pressure in diaphragm chamber 58 so that the diaphragm 56 is exposed to a pressure differential. In the case of gradual variation in pressure in line 52, due for example, to change in web tension, the pressure differential on the diaphragm 56 is of relativelysmall degree, so that the compressive force of spring 70 is insufficient to move the rod 66 to seat the contact arm 68. However, when a sudden change of back pressure is developed in line 52, such for example, as would be caused by the nozzle being brought in alignment with a flaw, i.e., hole or end out, in the web, the pressure in diaphragm chamber 58 will drop suddenly, while the pressure in diaphragm chamber 61 will drop more gradually. Under such conditions, the pressure differential on the diaphragm will be relatively large and will be suflicient to move the rod 66 to seat the contact arm 68.

A graphic illustration of the foregoing will be found in Fig. 3. Curve P5811 represents pressure condition in diaphragm chamber 58 under normal operating conditions, including a gradual drop in pressure such as may be attributable to reduction in web tension. Curve P60n represents pressure condition in diaphragm chamber 60 under normal operating conditions, including a gradual drop in pressure as in the case of curve P58n. The vertical distance between these two curves, i.e., PDn, represents the pressure differential acting upon the diaphragm 56, which is insuflicient to cause seating of contact arm 68 as heretoforediscussed. Curve P58 represents pressure condition in diaphragm chamber 58 upon detection of a flaw, i.e., hole in the fabric, which curve is very steep. Curve P60 represents pressure condition in diaphragm chamber 60 upon detecting of said flaw, which curve is more gradual in slope. The vertical distance between these two curves, i.e., PD represents the pressure differential acting upon diaphragm 56, which is sufficient to cause seating of contact arm 68, as heretofore discussed.

The scale of the coordinates of the graph of Fig. 3 is merely illustrative; other scale values may be more appropriate under any given conditions, or structural proportions. Also, the curves PSSn and P60n could slope upwardly, as in the case where web tension would gradually increase, while curves P58 and P60 could again rise sharply upwards if the nozzle overshot the flaw in the material due to inertia forces, which would be more likely in an actual installation. However, the graph does vividly illustrate the basic operating principle of the invention.

In Figs. 6-9 is illustrated a nozzle 82 which diifers from nozzle 16, only in that the first passageway is in the form of a slot 84, all other details thereof being similar or equivalent to the details of nozzle 16, as is evidenced by the use of the same identifying numerals. In arranging the nozzle 82 for operation, the length or long dimension of slot 84, is parallel with the travel of the web. One of the advantages of arranging the nozzle hole in slot form, is that a more pronounced signal is generated upon detection of an end out in the fabric.

Fig. 9 illustrates a modified form of detector nozzle switch means, as described hereinbefore. Assemblage 86, includes housing portions 88 and 90 which positionally maintain a diaphragm 92 to form diaphragm chambers 94 and 6, chamber 96 being of much greater volume than chamber 94. Actually, chamber 94 would correspond in volume to chamber 58 of diaphragm assembly 12, while chamber 96 would correspond in volume to chamber 60; plus the volume of volume chambers 62. A switch 98 mounted inside chamber 96 provides that part of the switch circuit as provided by contact arm 68, while a compression spring 100 affixed at one end to the diaphragm 92, serves. the same function as compression spring 79, of the first embodiment. An adjusting screw 102 is provided for regulating spring compression. Pipe or line 52 is arranged in communication with chamber 94 and also through valve 64 to the chamber 96. The nozzle 16 is positioned on line 52 near the diaphragm housings, so that the whole assemblage moves as a unit during web scanning operations.

Certain features are provided by the nozzle assemblage 86, merely, a more compact unit, and shorter line length which, among other things, improves operating performance. It will otherwise be apparent that the function of nozzle assemblage 86, provides advantages similar to the embodiment first described hereinbefore, and that both embodiments satisfy the objectives of the invention in every respect.

While the desensitizing means described has been in the form of a volume chamber 62, other forms of desensitizing arrangements may be utilized. For example, in certain installations, the use of the volume chamber may be dispensed with, and the valve 64 alone may be utilized to regulate air flow in the line leading to diaphragm chamber 60. In effect, any resistance which will provide unequal flow rates into or out of diaphragm chambers 58 and 60 may be satisfactory under given operating arrangements. Also, with equal flow resistances in the lines leading, to chambers 58 and 60, the use of disproportionate chamber sizes may also provide the desired effect.

The foregoing description has been given in detail without thought of limitation since the inventive principles involved are capable of assuming other forms without departing from the spirit of the invention or the scope of the following claims.

What is claimed is:

1. A detector for a knitting machine, comprising a nozzle formed to provide a passageway having an opening on a surface of the nozzle over which the fabric being formed in the machine is moved, means to supply pressurized fluid to said passageway, said fabric and the condition thereof determining the rate of fluid flow from said opening, a diaphragm assembly including a diaphragm arranged to partially define enclosed chambers of substantially equal volumes one on each side of the diaphragm, fluid conducting lines interconnecting said passageway and said chambers, means associated with said diaphragm for stopping said machine in response to a given movement of said diaphragm due to a pressure differential thereupon, and means to provide unlike fluid flow resistance in the aforesaid lines leading to said chambers.

2. A detector for a knitting machine which forms a continuous web of fabric, comprising a nozzle formed to provide a passageway having an opening on a surface of the nozzle over which the fabric being formed is moved, means to oscillate the nozzle transverse to the direction of Web travel, means to supply pressurized fluid to said passageway, said fabric and the condition thereof determining the rate of fluid flow from said opening, a diaphragm assembly including a diaphragm arranged to partially define enclosed chambers of substantially equal volumes one on each side of the diaphragm, fluid conducting lines interconnecting said passageway and said chambers, means associated with said diaphragm for stopping said machine in response to a. given movement of said diaphragm due to a pressure differential thereupon, and means to provide unlike fluid flow resistance in the aforesaid lines leading to said chambers.

3. A detector for a knitting machine operable for knitting a continuous web of fabric which machine has a motive means including an electric motor, comprising a nozzle formed to provide a passageway having an open ing on a surface of the nozzle over which the fabric be ing formed is moved, means to oscillate the nozzle transverse to the direction of web travel, means to supply compressed air to said passageway, said fabric and the condition thereof determining the rate of air flow from said opening, a diaphragm assembly including a diaphragm arranged to partially define enclosed chambers one on each side of the diaphragm, air conducting lines interconnecting said passageway and said chambers, a volume chamber interposed in one of the lines leading to one of said chambers, and switch means operable by movement of said diaphragm due to a given pressure differential thereupon to open a circuit of the electric motor to stop operation of said machine.

4. A detector for a knitting machine according to claim 3, wherein an air flow control valve is arranged to regulate flow of air in the line having the volume chamber.

5. A detector for a knitting machine according to claim 3, wherein said passageway is formed to provide a reduced diameter portion, said line connection with said passageway being between said reduced diameter portion and the passageway opening.

6. A detector for a knitting machine operable for knitting a continuous web of fabric which machine has a motive means including an electric motor, comprising a nozzle formed to provide a passageway having an opening on a surface of the nozzle over which the fabric being formed is moved, means to oscillate the nozzle transverse to the direction of web travel, means to supply compressed air to said passageway, said fabric and the condition thereof determining the rate of air flow from said opening, a diaphragm assembly including a diaphragm arranged to partially define enclosed chambers one on each side of the diaphragm, one of said chambers being larger in volume than the other of said chambers, air conducting lines interconnecting said passageway and said chambers; and switch means operable by movement of said diaphragm due to a given pressure differential thereupon to open a circuit of the electric motor to stop operation said machine.

7. A detector for a knitting machine according to claim 6, wherein said switch means is arranged in one of said chambers.

8. A detector for a knitting machine according to claim 7, wherein a flow control valve is arranged in the line leading to the larger of said chambers.

References Cited in the file of this patent UNITED STATES PATENTS 2,694,911 Peck Nov. 23, 1954 

